Objective C 和课堂上的魔法方法

发布于 2024-11-28 03:15:52 字数 43 浏览 3 评论 0 原文

Objective-C 是否提供了一种方法来拦截对不存在的类方法的调用？

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墨小沫ゞ 2024-12-05 03:15:52

您将要使用 forwardInitation 方法。当对对象调用不存在的选择器时，会自动调用它。此方法的默认行为是调用 doesNotRecognizeSelector:（它将调试信息输出到控制台），但您可以覆盖它以执行任何您想要的操作。 Apple 推荐的一种方法是让此方法将方法调用转发到另一个对象。

- (void)forwardInvocation:(NSInvocation *)anInvocation

请注意，forwardInitation 是一个相当昂贵的操作。 NSIncation 对象需要由框架创建并（可选）用于调用另一个实例上的选择器。如果您正在寻找一种（相对）更快的方法来检测不存在的选择器，那么您可以选择实现 forwardingTargetForSelector。

- (id)forwardingTargetForSelector:(SEL)aSelector

您应该Apple 文档对于如何有效地重写这些方法，有一些问题需要注意，特别是在缺少选择器的同一对象上重写 forwardInvocau 方法时。

The forwardInvocation method is what you are going to want to use. It is called automatically when a non-existent selector is called on an object. The default behavior of this method is to call doesNotRecognizeSelector:(which is what outputs debug information to your console), but you can override it do anything you want. One recommended approach by Apple is to have this method forward the method invocation to another object.

- (void)forwardInvocation:(NSInvocation *)anInvocation

Note that forwardInvocation is a fairly expensive operation. An NSInvocation object needs to be created by the framework and (optionally) used to invoke a selector on another instance. If you are looking for a (relatively) faster method of detecting non-existent selectors then you can choose to implement forwardingTargetForSelector instead.

- (id)forwardingTargetForSelector:(SEL)aSelector

You should Apple's documentation for how to override these methods effectively, there are some gotcha's to watch out for, particularly when overriding the forwardInvocation method on the same object that will have the missing selectors.